wpa_background

       IEEE 802.11i

WPA
       The original  security  mechanism  of  IEEE  802.11  standard  was  not
       designed  to  be strong and has proven to be insufficient for most net-
       works that require some kind of security. Task group  I  (Security)  of
       IEEE  802.11  working  group (http://www.ieee802.org/11/) has worked to
       address the flaws of the base standard and has  in  practice  completed
       its  work  in  May  2004. The IEEE 802.11i amendment to the IEEE 802.11
       standard was approved in June 2004 and published in July 2004.

       Wi-Fi Alliance (http://www.wi-fi.org/) used a draft version of the IEEE
       802.11i  work  (draft  3.0) to define a subset of the security enhance-
       ments that can be implemented with  existing  wlan  hardware.  This  is
       called  Wi-Fi  Protected Access<TM> (WPA). This has now become a manda-
       tory component of interoperability testing and  certification  done  by
       Wi-Fi  Alliance.  Wi-Fi  provides information about WPA at its web site
       (http://www.wi-fi.org/OpenSection/protected_access.asp).

       IEEE 802.11 standard defined wired equivalent privacy  (WEP)  algorithm
       for protecting wireless networks. WEP uses RC4 with 40-bit keys, 24-bit
       initialization  vector  (IV),  and  CRC32  to  protect  against  packet
       forgery. All these choices have proven to be insufficient: key space is
       too small against current attacks, RC4 key scheduling  is  insufficient
       (beginning  of  the pseudorandom stream should be skipped), IV space is
       too small and IV reuse makes attacks easier, there is no replay protec-
       tion,  and  non-keyed authentication does not protect against bit flip-
       ping packet data.

       WPA is an intermediate solution for the security issues. It uses Tempo-
       ral  Key Integrity Protocol (TKIP) to replace WEP. TKIP is a compromise
       on strong security and possibility to use existing hardware.  It  still
       uses  RC4 for the encryption like WEP, but with per-packet RC4 keys. In
       addition, it implements replay protection, keyed packet  authentication
       mechanism (Michael MIC).

       Keys  can be managed using two different mechanisms. WPA can either use
       an external authentication server (e.g., RADIUS) and EAP just like IEEE
       802.1X is using or pre-shared keys without need for additional servers.
       Wi-Fi calls these "WPA-Enterprise"  and  "WPA-Personal",  respectively.
       Both  mechanisms will generate a master session key for the Authentica-
       tor (AP) and Supplicant (client station).

       WPA implements a new key handshake (4-Way Handshake and Group Key Hand-
       shake)  for  generating and exchanging data encryption keys between the
       Authenticator and Supplicant. This handshake is  also  used  to  verify
       that  both  Authenticator  and  Supplicant know the master session key.
       These handshakes are identical regardless of the selected  key  manage-
       ment  mechanism  (only  the  method  for  generating master session key
       changes).

IEEE 802.11I / WPA2
       The design for parts of IEEE 802.11i that were not included in WPA  has
       finished  (May  2004) and this amendment to IEEE 802.11 was approved in

       This  program  is  dual-licensed  under  both the GPL version 2 and BSD
       license. Either license may be used at your option.



                               07 September 2010             WPA_BACKGROUND(8)
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